1. Field of the Invention
The present invention relates to a transfer method for an easily polymerizable substance like (meth)acrylic acid, (meth)acrylic ester, (meth)acrolein or the like, as well as for liquids containing such easily polymerizable substances, and to a facility therefore. More specifically, the present invention relates to a transfer method for an easily polymerizable substance and to a transfer facility therefore, which limit standing retention of the easily polymerizable substance in the feed pump, etc. inside the facility, and the generation of polymers that accompany such retention.
Priority is claimed on Japanese Patent Application No. 2002-92511, filed Mar. 28, 2002, the content of which is incorporated herein by reference.
2. Description of Related Art
Such easily polymerizable substances as (meth)acrylic acid, (meth)acrylic ester and (meth)acrolein undergo polymerization extremely readily. When manufacturing or handling these substances, polymerized substances arise from these and, in some cases, necessitate stoppage of the device or process.
When manufacturing (meth)acrylic acid, (meth)acrylic ester and (meth)acrolein, conventionally known countermeasures to the aforementioned problem include: i) adding a polymerization inhibitor such as hydroquinone, phenothiazine, etc.; and, further, ii) performing a surface polishing treatment inside the device in order to prevent adherence of solid matter such as polymer material or precipitate to the inside of the device; iii) cooling (or, in some cases, heating) the device from the outside; and iv) preventing stay of fluid or retention. However, the conventional technology has yet to be successful in fully preventing the generation or adherence of solid matter like polymer or precipitate material
When transferring an easily polymerizable substance such as (meth)acrylic acid, (meth)acrylic ester or (meth)acrolein, a feed pump disposed along the transfer passage is typically employed. An emergency or a back-up feed pump, provided in case of malfunction of the main feed pump, and an auxiliary feed pump, for temporarily increasing transfer capacity, (the term “reserve feed pump” being employed hereinafter for both), are provided in parallel to the aforementioned main feed pump. So that they begin operating immediately in the event of an emergency, at least one of reserve feed pumps is always connected to the transfer passage and is filled with the easily polymerizable substance.
FIG. 7 is a schematic structural diagram showing an example of a transfer facility for an easily polymerizable substance in which the two feed pumps are disposed in parallel. Feed pumps 13 and 14 are respectively provided to a first passage 11 and a second passage 12 which branch off from each other at the easily polymerizable substance inflow side, and converge at the easily polymerizable substance outflow side in the transfer facility. Respective check valves 15 and 16 are provided at positions downstream to feed pumps 13 and 14, so that when one of either feed pumps 13 and 14 is stopped, the easily polymerizable substance does not flow from the outflow to the inflow side through the passage of the halted feed pump, or does not flow backward. In addition, strainers 17 and 18 for removing foreign material are provided at a position upstream from feed pumps 13 and 14.
However, in an easily polymerizable substance transfer facility of this type, in which at least one of emergency and at least one of auxiliary feed pumps are provided, the easily polymerizable substance is retained in the reserve feed pump, which is held in the halted stated, and in its strainer and the passage for the pump and the strainer. As a result, generation of solid matter such as polymer, becomes a problem. When such polymer material is generated, it becomes impossible to use the easily polymerizable substance transfer facility, and operational anomalies occur as a result of the polymer material.
In addition, when it becomes necessary to immediately switch to the reserve feed pump in the case where transferring a high-temperature (at least 40° C., for example) easily polymerizable substance, it is possible for heat shock to occur at the moment the high-temperature easily polymerizable substance is introduced into the passage for the reserve feed pump due to the temperature difference between the easily polymerizable substance and the cooler pipes. As a result of this heat shock, leakage of the easily polymerizable substance from the connections between pipes may occur, leading in some cases to damage of the facility.